diff --git a/game.c b/game.c
index 18ae693..6ca3185 100644
--- a/game.c
+++ b/game.c
@@ -15,6 +15,10 @@ static const uint16_t _colors_1a0_data[] = {
 	0x1b0,0xbcf,0x1b2,0xfca,0x1b4,0x30a,0x1b6,0xa9a,0x1b8,0x900,0x1ba,0x666,0x1bc,0x747,0x1be,0x020
 };
 
+static const uint8_t _colors_cga[] = {
+	0x00, 0x00, 0x00, 0x55, 0xFF, 0xFF, 0xFF, 0x55, 0xFF, 0xFF, 0xFF, 0xFF
+};
+
 struct vars_t g_vars;
 
 void update_input() {
@@ -29,7 +33,7 @@ void update_input() {
 
 void do_title_screen() {
 	const uint32_t timestamp = g_sys.get_timestamp() + 20 * 1000;
-	load_img(g_res.amiga_data ? "blues.lbm" : "pres.sqz", GAME_SCREEN_W);
+	load_img(g_res.amiga_data ? "blues.lbm" : "pres.sqz", GAME_SCREEN_W, g_options.cga_colors ? 0 : -1);
 	fade_in_palette();
 	do {
 		update_input();
@@ -50,7 +54,7 @@ void do_select_player() {
 	int frame2 = 1;
 	const int color_rgb = 2;
 	const int colors_count = 25;
-	load_img(g_res.amiga_data ? "choix.lbm" : "choix.sqz", GAME_SCREEN_W);
+	load_img(g_res.amiga_data ? "choix.lbm" : "choix.sqz", GAME_SCREEN_W, g_options.cga_colors ? 1 : -1);
 	screen_load_graphics();
 	screen_clear_sprites();
 	do {
@@ -215,8 +219,7 @@ static void do_inter_screen_helper(int xpos, int ypos, int c) {
 static void do_inter_screen() {
 	static const uint8_t xpos[] = { 0xFA, 0x50, 0xF0, 0xC8, 0x50, 0x50 };
 	static const uint8_t ypos[] = { 0xAA, 0x37, 0x28, 0x5F, 0xA5, 0xAA };
-	load_img(g_res.amiga_data ? "inter.lbm" : "inter.sqz", GAME_SCREEN_W);
-	g_vars.screen_draw_h = GAME_SCREEN_H - 1;
+	load_img(g_res.amiga_data ? "inter.lbm" : "inter.sqz", GAME_SCREEN_W, g_options.cga_colors ? 9 : -1);
 	screen_clear_sprites();
 	if (g_vars.level > 1) {
 		for (int i = 0; i < g_vars.level - 1; ++i) {
@@ -297,7 +300,9 @@ void game_main() {
 		extern const uint8_t icon778e[]; // instrument level 5 (found)
 		g_res.spr_frames[144] = icon778e;
 	}
-	if (g_options.amiga_colors) {
+	if (g_options.cga_colors) {
+		g_sys.set_screen_palette(_colors_cga, 4);
+	} else if (g_options.amiga_colors) {
 		uint16_t palette[16];
 		for (int i = 0; i < 16; ++i) {
 			assert(_colors_1a0_data[i * 2] == 0x1a0 + i * 2);
diff --git a/game.h b/game.h
index 3191105..022b385 100644
--- a/game.h
+++ b/game.h
@@ -49,6 +49,7 @@ struct options_t {
 	bool amiga_colors;
 	bool amiga_status_bar;
 	bool dos_scrolling;
+	bool cga_colors;
 };
 
 extern struct options_t g_options;
@@ -155,8 +156,7 @@ struct vars_t {
 	int screen_tilemap_xoffset, screen_tilemap_yoffset;
 	int screen_tilemap_size_w, screen_tilemap_size_h;
 	int screen_scrolling_dirmask;
-	int screen_draw_h;
-	int screen_tile_lut[256];
+	uint16_t screen_tile_lut[128];
 	bool level_completed_flag;
 	bool play_level_flag;
 	bool game_over_flag;
@@ -177,7 +177,7 @@ struct vars_t {
 	bool inp_key_left;
 	bool inp_key_up_prev;
 	bool inp_key_down_prev;
-	bool inp_key_action;
+	bool inp_key_space_prev;
 	struct door_t doors[MAX_DOORS];
 	struct object_t objects[MAX_OBJECTS];
 	int vinyls_count;
diff --git a/level.c b/level.c
index f0b0656..1516f63 100644
--- a/level.c
+++ b/level.c
@@ -34,13 +34,14 @@ static const struct {
 	const int16_t *xpos;
 	const int16_t *ypos;
 	uint8_t music;
+	uint8_t cga_dither;
 } _levels[MAX_LEVELS] = {
-	{ "mag.ck1", "mag.ck2", "mag.sql", "magasin.bin", "avtmag.sqv", "enemi1.sqv", level_xpos_magasin, level_ypos_magasin, 1 },
-	{ "ent.ck1", "ent.ck2", "ent.sql", "entrepot.bin", "avtent.sqv", "enemi2.sqv", level_xpos_ent, level_ypos_ent, 2 },
-	{ "prison.ck1", "prison.ck2", "prison.sql", "prison.bin", "avtpris.sqv", "enemi3.sqv", level_xpos_prison, level_ypos_prison, 3 },
-	{ "egou.ck1", "egou.ck2", "egou.sql", "egou.bin", "avtegou.sqv", "enemi4.sqv", level_xpos_egou, level_ypos_egou, 1 },
-	{ "ville.ck1", "ville.ck2", "ville.sql", "ville.bin", "avtville.sqv", "enemi5.sqv", level_xpos_ville, level_ypos_ville, 2 },
-	{ "concert.ck1", "concert.ck2", "concert.sql", "concert.bin", "", "enemi6.sqv", level_xpos_concert, level_ypos_concert, 3 },
+	{ "mag.ck1", "mag.ck2", "mag.sql", "magasin.bin", "avtmag.sqv", "enemi1.sqv", level_xpos_magasin, level_ypos_magasin, 1, 3 },
+	{ "ent.ck1", "ent.ck2", "ent.sql", "entrepot.bin", "avtent.sqv", "enemi2.sqv", level_xpos_ent, level_ypos_ent, 2, 3 },
+	{ "prison.ck1", "prison.ck2", "prison.sql", "prison.bin", "avtpris.sqv", "enemi3.sqv", level_xpos_prison, level_ypos_prison, 3, 5 },
+	{ "egou.ck1", "egou.ck2", "egou.sql", "egou.bin", "avtegou.sqv", "enemi4.sqv", level_xpos_egou, level_ypos_egou, 1, 3 },
+	{ "ville.ck1", "ville.ck2", "ville.sql", "ville.bin", "avtville.sqv", "enemi5.sqv", level_xpos_ville, level_ypos_ville, 2, 7 },
+	{ "concert.ck1", "concert.ck2", "concert.sql", "concert.bin", "", "enemi6.sqv", level_xpos_concert, level_ypos_concert, 3, 8 },
 };
 
 static const struct {
@@ -68,13 +69,14 @@ void load_level_data(int num) {
 		// .avt
 		load_spr(_levels_amiga[num].ennemi, g_res.tmp, SPRITES_COUNT);
 	} else {
+		const int dither_pattern = g_options.cga_colors ? _levels[num].cga_dither : -1;
 		if (num == 0 && g_res.dos_demo) {
-			load_ck("demomag.ck1", 0x6000);
-			load_ck("demomag.ck2", 0x8000);
+			load_ck("demomag.ck1", 0x6000, dither_pattern);
+			load_ck("demomag.ck2", 0x8000, dither_pattern);
 			load_sql("demomag.sql");
 		} else {
-			load_ck(_levels[num].ck1, 0x6000);
-			load_ck(_levels[num].ck2, 0x8000);
+			load_ck(_levels[num].ck1, 0x6000, dither_pattern);
+			load_ck(_levels[num].ck2, 0x8000, dither_pattern);
 			load_sql(_levels[num].sql);
 		}
 		load_bin(_levels[num].bin);
@@ -269,11 +271,7 @@ static void do_level_redraw_tilemap(int xpos, int ypos) {
 		const uint8_t *ptr = lookup_sql(x, y + j);
 		for (int i = 0; i < w; ++i) {
 			const uint8_t num = *ptr++;
-			if (num >= 128) {
-				screen_draw_tile(g_vars.screen_tile_lut[num - 128], 4, i, j);
-			} else {
-				screen_draw_tile(g_vars.screen_tile_lut[num], 3, i, j);
-			}
+			screen_draw_tile(g_vars.screen_tile_lut[num & 0x7F], num & 0x80, i, j);
 		}
 	}
 	g_vars.screen_tilemap_size_w = w;
@@ -312,11 +310,7 @@ static void do_level_update_tiles_anim() {
 				*ptr = num;
 				t->unk16 = num;
 			}
-			if (num >= 128) {
-				screen_draw_tile(g_vars.screen_tile_lut[num - 128], 4, i, j);
-			} else {
-				screen_draw_tile(g_vars.screen_tile_lut[num], 3, i, j);
-			}
+			screen_draw_tile(g_vars.screen_tile_lut[num & 0x7F], num & 0x80, i, j);
 		}
 	}
 }
@@ -822,37 +816,7 @@ static void do_level_add_sprite3(struct object_t *obj) {
 void do_level_update_tile(int x, int y, int num) {
 	uint8_t *ptr = lookup_sql(x, y);
 	*ptr = num;
-
-	const int tile_xpos = g_vars.screen_tilemap_xorigin >> 4;
-	const int tile_ypos = g_vars.screen_tilemap_yorigin >> 4;
-
-	const int w = (TILEMAP_SCREEN_W / 16) * 2;
-	int _si = (x + tile_xpos) * 2 + g_vars.screen_tilemap_xoffset;
-	if (_si > w - 2) {
-		_si -= w;
-	}
-	const int h = (TILEMAP_SCREEN_H / 16) * 640;
-	int _di = (y - tile_ypos) * 640 + g_vars.screen_tilemap_yoffset;
-	if (_di > h - 640) {
-		_di -= h;
-	}
-	if (tile_xpos > x) {
-		return;
-	}
-	if (tile_xpos + (TILEMAP_SCREEN_W / 16) <= x) {
-		return;
-	}
-	if (tile_ypos > y) {
-		return;
-	}
-	if (tile_ypos + (TILEMAP_SCREEN_H / 16) <= y) {
-		return;
-	}
-	if (num >= 128) {
-		screen_draw_tile(g_vars.screen_tile_lut[num - 128], 4, _si / 2, _di / 640);
-	} else {
-		screen_draw_tile(g_vars.screen_tile_lut[num], 3, _si / 2, _di / 640);
-	}
+	screen_draw_tile(g_vars.screen_tile_lut[num & 0x7F], num & 0x80, x, y);
 }
 
 static void do_level_reset_tiles(struct object_t *obj, int dy) {
@@ -1010,7 +974,6 @@ static void do_level_update_grabbed_object(struct object_t *obj) {
 void do_level_update_panel_lifes(struct object_t *obj) {
 	struct object_t *obj39 = &g_vars.objects[OBJECT_NUM_PLAYER1];
 	struct object_t *obj40 = &g_vars.objects[OBJECT_NUM_PLAYER2];
-	g_vars.screen_draw_h = 172;
 	if (!g_vars.two_players_flag) {
 		static const uint16_t data[] = { 216, 232, 248, 264, 280, 296 };
 		for (int i = 0; i < obj->data51; ++i) {
@@ -1059,11 +1022,9 @@ void do_level_update_panel_lifes(struct object_t *obj) {
 			}
 		}
 	}
-	g_vars.screen_draw_h = TILEMAP_SCREEN_H;
 }
 
 static void do_level_update_panel_vinyls(struct object_t *obj) {
-	g_vars.screen_draw_h = 172;
 	if (obj->vinyls_count > 99) {
 		obj->vinyls_count -= 100;
 		if (!g_vars.two_players_flag && obj->data51 < 5) {
@@ -1085,12 +1046,10 @@ static void do_level_update_panel_vinyls(struct object_t *obj) {
 		}
 		g_vars.vinyls_count = obj->vinyls_count;
 	}
-	g_vars.screen_draw_h = TILEMAP_SCREEN_H;
 }
 
 static void do_level_update_panel_2nd_player() {
 	struct object_t *obj = &g_vars.objects[OBJECT_NUM_PLAYER2];
-	g_vars.screen_draw_h = 172;
 	if (obj->vinyls_count > 99) {
 		obj->vinyls_count = 0;
 		if (!g_vars.two_players_flag && obj->data51 < 5) {
@@ -1105,13 +1064,11 @@ static void do_level_update_panel_2nd_player() {
 		screen_draw_number(obj->vinyls_count, 280, 163, 2);
 		g_vars.vinyls_count = obj->vinyls_count;
 	}
-	g_vars.screen_draw_h = TILEMAP_SCREEN_H;
 }
 
 static void draw_level_panel() {
 	struct object_t *obj39 = &g_vars.objects[OBJECT_NUM_PLAYER1];
 	struct object_t *obj40 = &g_vars.objects[OBJECT_NUM_PLAYER2];
-	g_vars.screen_draw_h = 172;
 	g_vars.vinyls_count = 0;
 	if (!g_vars.two_players_flag) {
 		screen_draw_frame(g_res.spr_frames[123], 12, 320, 0, -12);
@@ -1162,7 +1119,6 @@ static void draw_level_panel() {
 			}
 		}
 	}
-	g_vars.screen_draw_h = TILEMAP_SCREEN_H;
 }
 
 void do_level_enter_door(struct object_t *obj) {
@@ -1246,27 +1202,27 @@ static void do_level_update_input(struct object_t *obj) {
 	} else {
 		triggers_update_tiles2(obj);
 	}
-	if (g_vars.inp_key_space != 0 && g_vars.inp_key_up != 0 && g_vars.inp_key_up_prev == 0 && !g_vars.player2_scrolling_flag) {
+	if (g_vars.inp_key_space && g_vars.inp_key_up && !g_vars.inp_key_up_prev && !g_vars.player2_scrolling_flag) {
 		obj->carry_crate_flag = 1;
 		do_level_enter_door(obj);
-		g_vars.inp_key_action = g_vars.inp_key_space;
+		g_vars.inp_key_space_prev = g_vars.inp_key_space;
 	}
-	if (g_vars.inp_key_space != g_vars.inp_key_action && g_vars.inp_key_up == 0) {
-		if (g_vars.inp_key_space != 0) {
+	if (g_vars.inp_key_space != g_vars.inp_key_space_prev && !g_vars.inp_key_up) {
+		if (g_vars.inp_key_space) {
 			obj->carry_crate_flag = 1;
 		}
-		g_vars.inp_key_action = g_vars.inp_key_space;
+		g_vars.inp_key_space_prev = g_vars.inp_key_space;
 	}
-	if (g_vars.inp_key_right != 0) {
+	if (g_vars.inp_key_right) {
 		obj->direction_lr |= OBJECT_DIRECTION_RIGHT;
 	}
-	if (g_vars.inp_key_left != 0) {
+	if (g_vars.inp_key_left) {
 		obj->direction_lr |= OBJECT_DIRECTION_LEFT;
 	}
 	_si = triggers_get_tile_type(obj->xpos16, obj->ypos16);
-	if (g_vars.inp_key_up != 0 && g_vars.inp_key_space == 0) {
+	if (g_vars.inp_key_up && !g_vars.inp_key_space) {
 		obj->direction_ud = OBJECT_DIRECTION_UP;
-		if (g_vars.inp_key_up_prev == 0 && obj->sprite_type != 0) {
+		if (!g_vars.inp_key_up_prev && obj->sprite_type != 0) {
 			obj->yfriction = 0;
 			_di = triggers_get_tile_type(obj->xpos16, obj->ypos16 - 2);
 			if (_di == 10 && (_si == 0 || _si == 1)) {
@@ -1285,7 +1241,7 @@ static void do_level_update_input(struct object_t *obj) {
 				}
 			}
 		}
-	} else if (g_vars.inp_key_down != 0) {
+	} else if (g_vars.inp_key_down) {
 		obj->direction_ud = 2;
 		if (!g_vars.inp_key_down_prev) {
 			obj->unk2B = 1;
@@ -1622,7 +1578,6 @@ static void do_level_handle_object_bonus_collision(struct object_t *obj, struct
 
 void do_level_player_hit(struct object_t *obj) {
 	if (obj->blinking_counter == 0) {
-		g_vars.screen_draw_h = 172;
 		if (obj->data51 > 0 && (g_options.cheats & CHEATS_UNLIMITED_ENERGY) == 0) {
 			--obj->data51;
 			do_level_update_panel_lifes(obj);
@@ -1630,7 +1585,6 @@ void do_level_player_hit(struct object_t *obj) {
 		if (obj->special_anim != 16) {
 			obj->blinking_counter = 75;
 		}
-		g_vars.screen_draw_h = TILEMAP_SCREEN_H;
 	}
 }
 
@@ -2127,7 +2081,7 @@ static void draw_foreground_tiles() {
 
 void do_level() {
 	static const int W = 320 / 16;
-	for (int tile_num = 0; tile_num < 256; ++tile_num) {
+	for (int tile_num = 0; tile_num < 128; ++tile_num) {
 		g_vars.screen_tile_lut[tile_num] = (tile_num / W) * 640 + (tile_num % W);
 	}
 	g_vars.screen_tilemap_w = level_dim[g_vars.level * 2];
@@ -2142,7 +2096,8 @@ void do_level() {
 	if (g_options.amiga_copper_bars) {
 		g_sys.set_copper_bars(_copper_data + g_vars.level * 18);
 	}
-	if (g_options.amiga_colors) {
+	if (g_options.cga_colors) {
+	} else if (g_options.amiga_colors) {
 		g_sys.set_palette_amiga(_colors_data + g_vars.level * 16, 0);
 	}
 	g_vars.inp_keyboard[0xB9] = 0; // SPACE
@@ -2152,7 +2107,6 @@ void do_level() {
 	g_vars.level_completed_flag = 0;
 	g_vars.quit_level_flag = 0;
 	g_vars.player2_scrolling_flag = 0;
-	g_vars.screen_draw_h = TILEMAP_SCREEN_H;
 	g_vars.found_music_instrument_flag = 0;
 	render_set_sprites_clipping_rect(0, TILEMAP_OFFSET_Y, TILEMAP_SCREEN_W, TILEMAP_SCREEN_H);
 	bool screen_transition_flag = true;
diff --git a/main.c b/main.c
index 6bc67b6..8bb6ed2 100644
--- a/main.c
+++ b/main.c
@@ -37,6 +37,7 @@ int main(int argc, char *argv[]) {
 	g_options.amiga_colors = true;
 	// g_options.amiga_status_bar = true;
 	g_options.dos_scrolling = false;
+	// g_options.cga_colors = true;
 	const char *data_path = DEFAULT_DATA_PATH;
 	int scale_factor = DEFAULT_SCALE_FACTOR;
 	const char *scale_filter = DEFAULT_SCALE_FILTER;
diff --git a/resource.c b/resource.c
index 1f78b83..00a2503 100644
--- a/resource.c
+++ b/resource.c
@@ -23,6 +23,11 @@ void res_init(int vga_size) {
 	if (!g_res.avt_sqv) {
 		print_error("Failed to allocate avt buffer, %d bytes", AVT_SQV_SIZE);
 	}
+	static const int CGA_SIZE = 160 * 200;
+	g_res.cga = (uint8_t *)malloc(CGA_SIZE);
+	if (!g_res.cga) {
+		print_error("Failed to allocate cga buffer, %d bytes", CGA_SIZE);
+	}
 	const int tmp_size = 32000 + vga_size;
 	g_res.tmp = (uint8_t *)malloc(tmp_size);
 	if (!g_res.tmp) {
@@ -64,6 +69,8 @@ void res_fini() {
 	g_res.avt_sqv = 0;
 	free(g_res.tmp);
 	g_res.tmp = 0;
+	free(g_res.cga);
+	g_res.cga = 0;
 	free(g_res.vga);
 	g_res.vga = 0;
 	free(g_res.tiles);
@@ -88,6 +95,60 @@ int read_compressed_file(const char *filename, uint8_t *dst) {
 	return unpack(filename, dst);
 }
 
+extern const uint8_t dither_cga_table[];
+
+static void dither_cga(int num, uint8_t *dst) {
+	const uint8_t *_bx = dither_cga_table + num * 32;
+	for (int i = 0; i < 256; ++i) { // even lines
+		const uint8_t a = _bx[(i & 15) * 2];     // 0x20 | 0x10
+		const uint8_t b = _bx[(i >> 4) * 2 + 1]; // 0x80 | 0x40
+		const uint8_t tmp = ((b & 3) << 2) | (a & 3);
+		dst[0x100 + i] = tmp << 4;
+		dst[        i] = tmp;
+	}
+	for (int i = 0; i < 256; ++i) { // odd lines
+		const uint8_t a = _bx[(i & 15) * 2 + 1]; // 0x20 | 0x10
+		const uint8_t b = _bx[(i >> 4) * 2];     // 0x80 | 0x40
+		const uint8_t tmp = ((b & 3) << 2) | (a & 3);
+		dst[0x300 + i] = tmp << 4;
+		dst[0x200 + i] = tmp;
+	}
+	for (int i = 0; i < 256; ++i) {
+		uint8_t mask = i;
+		static const uint8_t lut[] = { 1, 0, 3, 2 };
+		for (int j = 0; j < 4; ++j) {
+			dst[0x400 + lut[j]] = ((mask & 1) << 7) | ((mask & 2) << 2); // 0x80 | 0x08
+			mask >>= 2;
+		}
+		dst += 4;
+	}
+}
+
+static void copy_cga(const uint8_t *src, uint8_t *di, uint8_t *dither_temp) {
+	for (int y = 0; y < 200; ++y) {
+		for (int x = 0; x < 40; ++x) {
+			int a = 0;
+			int d = 0;
+			for (int i = 0; i < 4; ++i) {
+				const int b = src[i * 40] * 4;
+				a |= READ_LE_UINT16(dither_temp + 0x400 + b) >> (3 - i);
+				d |= READ_LE_UINT16(dither_temp + 0x402 + b) >> (3 - i);
+			}
+			const uint8_t *p = dither_temp + (y & 1) * 0x200;
+			uint8_t _cl = p[a & 255] | p[0x100 + (a >> 8)];
+			uint8_t _ch = p[d & 255] | p[0x100 + (d >> 8)];
+			for (int i = 0; i < 4; ++i) {
+				*di++ = _ch & 3; _ch >>= 2;
+			}
+			for (int i = 0; i < 4; ++i) {
+				*di++ = _cl & 3; _cl >>= 2;
+			}
+			++src;
+		}
+		src += 120;
+	}
+}
+
 static void decode_bitplane_scanline(const uint8_t *src, int depth, int w, uint8_t *dst) {
 	const int plane_size = w / depth;
 	for (int x = 0; x < plane_size; ++x) {
@@ -106,7 +167,7 @@ static void decode_bitplane_scanline(const uint8_t *src, int depth, int w, uint8
 	}
 }
 
-static void load_iff(const uint8_t *data, uint32_t size, uint8_t *dst, int dst_pitch) {
+static void load_iff(const uint8_t *data, uint32_t size, uint8_t *dst, int dst_pitch, int cga_dither_pattern) {
 	print_debug(DBG_RESOURCE, "load_iff size %d", size);
 	if (data && memcmp(data, "FORM", 4) == 0) {
 		int offset = 12;
@@ -147,15 +208,19 @@ static void load_iff(const uint8_t *data, uint32_t size, uint8_t *dst, int dst_p
 				while (i < len && offset < 32000) {
 					int code = (int8_t)buf[i++];
 					if (code != -128) {
+						const int scanline_offset = offset % 160;
 						if (code < 0) {
 							code = 1 - code;
-							memset(scanline + offset % 160, buf[i], code);
+							memset(scanline + scanline_offset, buf[i], code);
 							++i;
 						} else {
 							++code;
-							memcpy(scanline + offset % 160, buf + i, code);
+							memcpy(scanline + scanline_offset, buf + i, code);
 							i += code;
 						}
+						if (!(cga_dither_pattern < 0)) {
+							memcpy(g_res.cga + offset, scanline + scanline_offset, code);
+						}
 						offset += code;
 						if ((offset % 160) == 0) {
 							decode_bitplane_scanline(scanline, 4, 160, dst + y * dst_pitch);
@@ -169,6 +234,12 @@ static void load_iff(const uint8_t *data, uint32_t size, uint8_t *dst, int dst_p
 			offset += 8 + len;
 		}
 	}
+	if (!(cga_dither_pattern < 0)) {
+		uint8_t dither_temp[2048];
+		memset(dither_temp, 0, sizeof(dither_temp));
+		dither_cga(cga_dither_pattern, dither_temp);
+		copy_cga(g_res.cga, dst, dither_temp);
+	}
 }
 
 void load_avt(const char *filename, uint8_t *dst, int offset) {
@@ -237,7 +308,7 @@ void load_blk(const char *filename) {
 	read_file(filename, g_res.tiles, 256 * 16 * 8);
 }
 
-void load_ck(const char *filename, uint16_t offset) {
+void load_ck(const char *filename, uint16_t offset, int dither_pattern) {
 	const int size = read_compressed_file(filename, g_res.tmp);
 	switch (offset) {
 	case 0x6000: // page3
@@ -250,11 +321,13 @@ void load_ck(const char *filename, uint16_t offset) {
 		print_error("Unexpected offset 0x%x in load_ck()", offset);
 		break;
 	}
-	load_iff(g_res.tmp, size, g_res.tiles + offset, 640);
-	g_sys.set_screen_palette(g_res.palette, 16);
+	load_iff(g_res.tmp, size, g_res.tiles + offset, 640, dither_pattern);
+	if (dither_pattern < 0) {
+		g_sys.set_screen_palette(g_res.palette, 16);
+	}
 }
 
-void load_img(const char *filename, int screen_w) {
+void load_img(const char *filename, int screen_w, int dither_pattern) {
 	int size;
 	const char *ext = strrchr(filename, '.');
 	if (ext && strcmp(ext + 1, "lbm") == 0) {
@@ -263,8 +336,10 @@ void load_img(const char *filename, int screen_w) {
 		size = read_compressed_file(filename, g_res.tmp);
 	}
 	assert(size <= 32000);
-	load_iff(g_res.tmp, size, g_res.tmp + 32000, screen_w);
-	g_sys.set_screen_palette(g_res.palette, 16);
+	load_iff(g_res.tmp, size, g_res.tmp + 32000, screen_w, dither_pattern);
+	if (dither_pattern < 0) {
+		g_sys.set_screen_palette(g_res.palette, 16);
+	}
 	g_sys.update_screen(g_res.tmp + 32000, 0);
 	memcpy(g_res.vga, g_res.tmp + 32000, g_res.vga_size);
 }
diff --git a/resource.h b/resource.h
index b8616bc..8fe3aa5 100644
--- a/resource.h
+++ b/resource.h
@@ -39,6 +39,7 @@ struct resource_data_t {
 	const uint8_t *spr_frames[MAX_SPR_FRAMES];
 	uint8_t palette[16 * 3];
 	struct trigger_t triggers[MAX_TRIGGERS];
+	uint8_t *cga;
 	uint8_t *vga;
 	int vga_size;
 	uint8_t *tiles;
@@ -56,8 +57,8 @@ extern int	read_compressed_file(const char *filename, uint8_t *dst);
 extern void	load_avt(const char *filename, uint8_t *dst, int offset);
 extern void	load_bin(const char *filename);
 extern void	load_blk(const char *filename);
-extern void	load_ck(const char *filename, uint16_t offset);
-extern void	load_img(const char *filename, int screen_w);
+extern void	load_ck(const char *filename, uint16_t offset, int dither_pattern);
+extern void	load_img(const char *filename, int screen_w, int dither_pattern);
 extern void	load_m(const char *filename);
 extern void	load_spr(const char *filename, uint8_t *dst, int offset);
 extern void	load_sqv(const char *filename, uint8_t *dst, int offset);
diff --git a/screen.c b/screen.c
index b02ca70..fb6c1d1 100644
--- a/screen.c
+++ b/screen.c
@@ -53,9 +53,11 @@ void fade_out_palette() {
 }
 
 void screen_adjust_palette_color(int color, int b, int c) {
-	g_res.palette[color * 3 + b] += c;
-	screen_vsync();
-	g_sys.set_screen_palette(g_res.palette, 16);
+	if (!g_options.cga_colors) {
+		g_res.palette[color * 3 + b] += c;
+		screen_vsync();
+		g_sys.set_screen_palette(g_res.palette, 16);
+	}
 }
 
 void screen_vsync() {
@@ -115,7 +117,7 @@ void screen_clear(int a) {
 
 void screen_draw_tile(int tile, int type, int x, int y) {
 	const uint8_t *src = g_res.tiles + tile * 16;
-	if (type == 4) {
+	if (type != 0) {
 		src += 320;
 	}
 	x = g_vars.screen_tilemap_xoffset + x * 16;
diff --git a/staticres.c b/staticres.c
index 350d62f..4459ded 100644
--- a/staticres.c
+++ b/staticres.c
@@ -1785,3 +1785,25 @@ const uint8_t icon778e[] = {
 	0x86,0x5d,0x20,0x04,0x9a,0xbd,0x80,0x05,0x80,0x1d,0x80,0xe5,0xa1,0x5d,0x00,0x00,
 	0x00,0x0c,0x00,0x10
 };
+const uint8_t dither_cga_table[] = {
+	0x00,0x00,0x55,0x55,0xAA,0xAA,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,0xAA,0xAA,0xFF,0xFF,
+	0x00,0x00,0x55,0x55,0xFF,0xFF,0xAA,0xAA,0x00,0x00,0x55,0x55,0xFF,0xFF,0xAA,0xAA,
+	0x00,0x00,0xAA,0xAA,0x55,0x55,0x55,0x55,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,
+	0x00,0x00,0xFF,0xFF,0xFF,0xFF,0x00,0x00,0x55,0x55,0xFF,0xFF,0xAA,0xAA,0xFF,0xFF,
+	0x00,0x00,0xAA,0xAA,0x55,0x55,0x55,0x55,0x00,0x00,0xFF,0xFF,0xAA,0xAA,0xAA,0xAA,
+	0x55,0x55,0x55,0x55,0x55,0x55,0x00,0x00,0xFF,0xFF,0xAA,0x00,0x55,0x55,0xFF,0xFF,
+	0x00,0x00,0xAA,0xAA,0x55,0xAA,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,
+	0x55,0x55,0x00,0x00,0xAA,0xAA,0x00,0x00,0x55,0x55,0xAA,0x00,0x00,0x00,0xFF,0xFF,
+	0x00,0x00,0xAA,0xAA,0xAA,0xAA,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,
+	0x55,0x55,0x00,0x00,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xAA,0xAA,0x00,0x00,0xFF,0xFF,
+	0x00,0x00,0xAA,0xAA,0xFF,0xFF,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,
+	0x55,0x55,0x00,0x00,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xAA,0xAA,0x00,0x00,0xFF,0xFF,
+	0x00,0x00,0x00,0x00,0xAA,0xAA,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,
+	0x55,0x55,0x00,0x00,0xAA,0xAA,0x00,0x00,0x55,0x55,0xAA,0xAA,0xAA,0xAA,0xFF,0xFF,
+	0x00,0x00,0xFF,0xFF,0x00,0x00,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0xAA,0xAA,
+	0x55,0x55,0x55,0x55,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xAA,0xAA,0xAA,0xAA,0xFF,0xFF,
+	0x00,0x00,0xAA,0xAA,0x55,0x55,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0x00,0x00,0xAA,0xAA,
+	0x55,0x55,0xAA,0xAA,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0x55,0x55,0xFF,0xFF,0xFF,0xFF,
+	0x00,0x00,0x00,0x00,0xAA,0xAA,0x00,0x00,0x00,0x00,0xFF,0xFF,0xFF,0xFF,0x55,0x55,
+	0x55,0x55,0x00,0x00,0xAA,0xAA,0x00,0x00,0xFF,0xFF,0xAA,0xAA,0x55,0x55,0xFF,0xFF
+};